Preparation of Fe2O3 modified kaolin and application in heterogeneous electro-catalytic oxidation of enoxacin

Abstract

Preparation and use of an iron containing catalyst, Fe2O3 modified kaolin (Fe2O3-KLN), was investigated to develop a heterogeneous electro-Fenton process for the electrochemical oxidation of enoxacin (ENXN). The characterizations of the prepared Fe2O3-KLN were performed using different methods. Mineralization efficiency of the electro-Fenton method increased in the presence of Fe2O3-KLN catalyst. The experimental variables that affect the efficiency of heterogeneous electro-Fenton treatment were investigated. Mineralization rates of ENXN reached its maximal value in the presence of 0.3g Fe2O3-KLN at 300mA. While the mineralization efficiency of ENXN was much higher in pH values of 2.0 and 3.0, the total mineralization of ENXN was also observed at pH values of 5.1 and 7.1. A very small decrease (0.5%) was found in the activity of Fe2O3-KLN after five runs. Characterization studies showed that the change in the morphology and chemical structure of Fe2O3-KLN during the experiments was negligible. The amount of leached iron (∼0.006mM) revealed that hydroxyl radicals were mainly produced by heterogeneous reactions of surface iron species. GC–MS, HPLC and LC–MS analysis allowed the identification of some of organic oxidation intermediates. Inorganic oxidation intermediates (F−, NO3− and NH4+) were identified by IC analysis. An oxidation pathway was proposed for the mineralization of ENXN.